The present invention relates to a novel sulfonated product of a butadiene or isoprene oligomer and a process for the production thereof. More particularly, it relates to a sulfonated product of the following formula: ##STR2## wherein one of R.sub.1 and R.sub.1 ' is hydrogen or methyl and another one is hydrogen; R.sub.2 is hydrogen or methyl; one of X.sub.1 and X.sub.2 is --SO.sub.3 M and another one is hydrogen; a and b are each an integer satisfying the conditions: n = a + b, 2 &lt; n &lt; 40 and 0 &lt; b; M is hydrogen, Na, K, Li or --NR.sub.3 R.sub.4 R.sub.5 R.sub.6 ; and R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each hydrogen or an alkyl having 1 to 6 carbon atoms, and a process for the production of the sulfonated product.
Sulfonic acid is a strong acid comparable to hydrochloric acid and a salt of sulfonic acid is water-soluble. The sulfonic acid or a salt thereof can be used for giving some specific properties to organic compounds by reacting therewith, and hence, the sulfonic acid or its derivatives are very valuable as an intermediate for the preparation of compounds useful in surfactants or dyestuffs industries and other organic industries. Extensive research has hitherto been done on aromatic sulfonated products, but only a small amount of research has been done on aliphatic sulfonated products.
During the present inventors' studies on liquid butadiene and isoprene oligomers and derivatives thereof, they have aimed at the sulfonic acid derivative of these butadiene and isoprene oligomers which have specific properties and have made extensive studies on the process for the production thereof and also on the properties thereof. As the a result, it has been found that some novel sulfonated products of liquid polybutadiene show excellent properties as mentioned hereinafter, and further that some novel sulfonated products of isoprene oligomers also show excellent properties.
Some sulfonated products of polymers, such as a polymer of vinylsulfonic acid and a sulfonated product of polystyrene are known, but there is not known any other sulfonated product of a polymer having a chemically clear structure. For instance, some sulfonated products of polyolefins such as polyethylene, polypropylene or polyisobutene are described in Italian Patent Specification No. 591,501, but the sulfonation has been done for the purpose of accelerating the vulcanization of the high polymers and these compounds do not have a clear structure.
Some compounds similar to the sulfonated products, such as a sulfuric acid ester of polyvinyl alcohol, have also been known, but these compounds are an ester of an alcohol and sulfuric acid and are clearly distinguished from the sulfonated products.
An object of the present invention is to provide novel sulfonated products of butadiene or isoprene oligomer of the formula (I). Another object of the present invention is to provide a process for the production of the sulfonated products (I). These and other objects of the invention will be apparent from the following description.
The sulfonated products of the formula (I) can be produced by various processes, but is usually produced by first produced an oligomer of butadiene or isoprene and then sulfonating the oligomer.
It is known that highly unsaturated compounds such as polybutadiene are reacted with sulfites to give sulfonated products (cf. Japanese Patent Publication No. 6834/1974). In this process, polybutadiene containing a vinyl group in the side chain is used as the starting material. However, according to the present inventors' study, it is not necessarily required to use such a compound containing a double bond in the side chain. Generally, in the case of the reaction of high molecular weight compounds wherein the double bond participates, the reaction effectively proceeds when the double bond is contained in the side chain of the reactants. It has now been found that, even if the polymers having the double bond in the main chain, such as high 1,4-type polybutadiene, are used as the reactant, they can be sulfonated by reacting them with sulfites, and further that the sulfonated products thus obtained have various excellent properties as mentioned hereinafter.
Moreover, according to the present invention, when a polymer containing a terminal double bond in addition to the double bond in the main chain is used as the starting material, the positioning of the sulfonyl group in the molecule can be controlled by utilizing the difference of the reactivity between the double bond and the sulfites.
When the starting material is a polymer having repeating units of the same chemical structure containing a vinyl bond, as disclosed in Japanese Patent Publication No. 6834/1974, the addition reaction thereof with sulfites proceeds at random, and hence, the positioning of the sulfonyl groups can not be controlled and shows a statistical distribution. On the contrary, when the starting material is a polybutadiene having no vinyl group in the side chain, as in the present invention, there can be produced a sulfonated product wherein the sulfonyl group is preferentially combined to the terminal of the molecule. Moreover, according to the present invention, the double bonds contained in the main chain of the polybutadiene can almost be retained without reacting with the sulfites, and hence, the resulting sulfonated products have a specific structure containing unsaturated bonds in the main chain.
The addition reaction of sulfites to unsaturated bonds has been widely studied. The rate of the addition reaction of sulfites varies depending on the kinds of structures of the compounds containing double bond (cf. Charles J. Norton et al, The Journal of Organic Chemistry, page 4158, 1968). The reaction rate will be slower in the order as shown in the following scheme: ##STR3##
Taking into consideration these prior arts, the present inventors have succeeded in the production of novel sulfonated products by producing an oligomer of butadiene or isoprene which has no vinyl group in the side chain and then preferentially adding sulfites to the terminal double bond. It has never been known that such a sulfonated product can be produced by adding sulfites to the polymer having no double bond in the side chain without reacting the double bond in the main chain and thereby the positioning of the sulfonyl groups in the molecule can be controlled. Moreover, according to the present invention, the desired sulfonated products can easily be produced without complicated side reaction or significant coloring of the product and without using any specific apparatus.
The starting butadiene or isoprene oligomers used in the present invention may be produced by known processes as disclosed in Japanese Laid Open Publication (without examination) Nos. 89788/1974 and 115189/1974. The oligomers include the liquid butadiene or isoprene oligomers comprising predominantly the compound containing double bond in the main chain of the following formula: ##STR4## wherein one of R.sub.1 and R.sub.1 ' is hydrogen or methyl and another one is hydrogen; R.sub.2 is hydrogen or methyl; and l is an integer satisfying the condition: 2.ltoreq.l.ltoreq.40. 3.ltoreq.l.ltoreq.8 is preferred because of the better power of emulsification.
These oligomers have the structure that ethylene or propylene is bonded to the terminal of a lower polymer of butadiene or isoprene.
The oligomers produced by the process have a wide range of molecular weight distribution and have larger contents of the compounds having a higher molecular weight than that of the compounds which are suitable for the preparation of synthetic detergents. When the sulfonated product of the present invention is used for the preparation of synthetic detergents, it is preferable to produce a product having a narrower molecular weight distribution by controlling the polymerization reaction so as to increase the reaction product having a lower degree of polymerization and further fractionating the reaction product. For instance, the oligomer produced by the process as hereinafter described in Example 1 contains predominantly the compound of the formula (II) wherein R.sub.1 and R.sub.1 ' are each hydrogen and R.sub.2 is methyl, and when this oligomer is subjected to rectification and gel permeation chromatography, the products as shown in the following Table 1 can be obtained.
Table 1 ______________________________________ Viscos- Refrac- l in the Molec- ity at Boiling Specific tive formula ular* 30.degree. C point gravity index (II) weight (cp) (.degree. C) (d.sup.25) (n.sub.D .sup.25) ______________________________________ 2 150 1.5 51 (2mmHg) 0.770 1.449 3 204 4.3 93 (2 mmHg) 0.797 1.458 4 260 5.2 156 (2 mmHg) 0.821 1.486 5 340 10.4 210 (0.04 0.867 1.504 mmHg) ______________________________________
The oligomer produced by the polymerization may be fractionated by a conventional method to give the first fraction (boiling point: not higher than 130.degree. C./40 mmHg), the second fraction (boiling point: 60.degree.-160.degree. C./1 mmHg), and the residue, and the suitable fraction is used as the starting oligomer in accordance with the desired utility.
The sulfites used as another reactant in the present invention include hydrogensulfites, metasulfites or sulfites of alkali metals, alkaline earth metals, ammonia, organic amines or quaternary ammonium bases (e.g. sodium hydrogensulfite, potassium hydrogensulfite, calcium hydrogensulfite, ammonium hydrogensulfite, sodium metasulfite, potassium metasulfite, sodium sulfite, potassium sulfite, calcium sulfite, ammonium sulfite), which may be used alone or in a mixture thereof. Alkali metal salts (e.g. sodium, potassium or lithium salt) are usually used. These salts may be used in an amount of 1 mol to 2(l + 1) mol, wherein l means the same as defined in the formula (II), to one mol of the oligomer in the sulfonation reaction, i.e. in a molar amount equivalent or double to the number of the double bond to which the sulfonyl group is introduced.
In the sulfonation of the oligomer in the present invention, a catalyst is not necessarily used, but use of an inorganic oxidizing catalyst is usually effective for shortening the reaction time. Suitable examples of the inorganic oxidizing catalyst are various metal salts of nitric acid, nitrous acid, chromic acid or chloric acid, such as alkali metal salts (e.g. sodium, potassium, lithium or rubidium salt), alkaline earth metal salts (e.g. beryllium, magnesium, calcium, zinc, cadmium or mercury salt), or other metal salts (e.g. iron, cobalt, nickel, chromium or aluminum salt) or ammonium salt. Among these salts, the salts of nitric acid are particularly effective. Oxygen or oxygen-containing gases are also useful as the catalyst. The catalyst is preferably used in an amount of 1/5 to 1/100 mol, more preferably 1/8 to 1/20 mol, to one mol of the starting sulfite.
The sulfonation of the present invention may be carried out in the absence or presence of a solvent, but it is preferable to conduct the reaction in an appropriate solvent for proceeding with the reaction both uniformly and smoothly. Suitable examples of the solvent are water, lower alcohols (e.g. methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, tert-butyl alcohol), lower glycols (e.g. ethylene glycol, propylene glycol), ketones (e.g. acetone, methyl ethyl ketone), ethers (e.g. ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, dioxane), esters (e.g. ethyl acetate), or the like, which may be used alone or in a combination of two or more thereof. A mixed solvent of water and a lower alcohol, particularly water and propyl alcohol, is preferable. The amount of the solvent is not necessarily specified, but the ratio of solvent/oligomer may preferably be in the range of 10/1 to 1/1 by weight, more preferably 8/1 to 3/1 by weight. In case of using a mixed solvent of water and a lower alcohol, the ratio of alcohol/water may preferably be in the range of 10/1 to 1/1 by weight, more preferably 5/1 to 3/1 by weight.
When water or a mixed solvent of water and other organic solvent is used, the reaction proceeds at a pH value of 2 to 9, but it is preferable to control the pH value in the reaction system in the range of 5 to 7 by using a pH regulator in order to prevent undesirable side reaction and to decrease the production of inorganic salts.
The sulfonation may be carried out at a reaction temperature of 30.degree. to 200.degree. C., preferably 60.degree. to 150.degree. C., more preferably 90.degree. to 120.degree. C., under atmospheric pressure or under pressure. The sulfonation reaction is usually completed within 2 hours at 120.degree. C. When a solvent is used, it is preferable to control the reaction conditions so that the solvent is maintained in liquid state.
In order to obtain the sulfonated products in the form of a free sulfonic acid derivative [i.e. M is hydrogen in the formula (I)], the reaction may be carried out at a low pH value. However, it will be preferable to desalt the sodium or potassium salt of the starting sulfites or the salt of the sulfonated product. The desaltation may be carried out by conventional methods, preferably dialysis or treatment with an ion exchange resin. For instance, a cationic exchange resin which is available commercially is introduced into a column and is modified into H type, and thereto an aqueous solution of a salt of a sulfonated product is continuously passed through, and thereby the salt of the sulfonated product can be converted into the free sulfonic acid derivative.
Besides, in order to obtain the sulfonated products in the form of an ammonium salt or quaternary ammonium salt of the formula: --NR.sub.3 R.sub.4 R.sub.5 R.sub.6 wherein R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are as defined above, the free sulfonic acid derivative obtained above is neutralized with aqueous ammonia or an aqueous solution of a quaternary ammonium hydroxide of the formula: NR.sub.3 R.sub.4 R.sub.5 R.sub.6 (OH). Suitable examples of the quaternary ammonium hydroxide are tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, tetrabutyl ammonium hydroxide, or the like.
The sulfonated products thus obtained are usually white or faint yellow, solid or grease-like material, while it depends on the physical properties and molecular weight of the starting butadiene or isoprene oligomers and further on the numeral of the sulfonyl group combined thereto. Besides, the sulfonated products are usually easily soluble in water, soluble in polar solvents such as lower alcohols, or dimethylsulfoxide, and insoluble in other organic solvents. However, the solubility of the product may be variable depending on the various factors, such as the molecular weight of the starting oligomers, the numeral of the sulfonyl group combined thereto or the kind of cation which forms the salt, and there can also be produced a product which is insoluble in water and soluble in organic solvents.
The novel sulfonated products of the present invention have a specific chemical structure and specific properties and hence are valuable for various utilities.
For instance, the sulfonated products are useful as a surfactant for the preparation of emulsifiers, dispersing agents and wetting agents. The products contain many double bonds in the main chain thereof, and hence, they are easily decomposable and are valuable as a surfactant having no problem of environmental pollution.
The sulfonated products have a particularly excellent hard water resistance, and hence, when they are used for the preparation of synthetic detergents, they show an excellent effect as a builder. Thus, the products are valuable for the preparation of detergents having low phosphorus content and having no problem of environmental pollution. The excellent hard water resistance of the present sulfonated products may be owing to the same principle as that of .alpha.-olefin sulfonate which shows a higher resistance to hard water than that of an alkanesulfonate, i.e., owing to the mechanism that the heavy metals contained in the hard water are hindered between the double bond of the molecule and the sulfonyl group and the mechanism that the affinity to the dirt is improved by the integrity of the molecule due to the double bond in the molecule.
When the sulfonated products are used as an emulsifier for emulsion polymerization, the reactive double bond contained therein functions to combine with the polymer and thereby prevent the isolation of the emulsifier from the emulsion particles. Moreover, when the emulsion produced by using the sulfonated products as the emulsifier is used as a paint, the paint is crosslinked by air oxidization thereof during the forming of the coating film, and thereby, the water resistance of the coating film is improved.
Furthermore, when the sulfonated products are combined with high molecular weight compounds via the reactive double bond, owing to the polarity of the sulfonyl group contained in the products, they can give to the high molecular weight compounds various excellent properties, such as antistatic properties, conductivity, water absorption properties, dyeability and stainproofing properties, and hence, they can be used for various industrial utilities, such as plastics, fibers and printing materials, as well as paints.
The performances of the sulfonated products may optionally be varied by hydrogenating the starting oligomers or the sulfonated products in accordance with the desired utilities.
The present invention is illustrated by the following Examples but is not limited thereto.